Pipeline relocation foundation pit support and construction method under complex environment

Abstract

The application provides a pipeline relocation foundation pit supporting and construction method in a complex environment, and belongs to the technical field of building construction, and comprises the following steps: S100, foundation pit structure design; S200, foundation pit excavation construction; S300, foundation pit supporting construction; S400, foundation pit bottom sealing; and S500, pipeline relocation; the method does not use large mechanical equipment, has no clearance requirement, can protect the pipeline, and can minimize the influence of the pipeline; and due to the use of the step-by-step excavation and step-by-step pouring of the arm supporting construction process, the foundation pit arm forms an integral structure, the foundation pit has high stability, the safety risk of the foundation pit is greatly reduced, and through the arrangement of the settlement monitoring points in the foundation pit, the real-time monitoring in the construction process verifies that the foundation pit designed and constructed through the method meets the design settlement requirement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building construction, in particular to a pipeline relocation foundation pit support and construction method in complex environment. BACKGROUND

[0002] With the acceleration of urbanization process, subway construction projects are increasing, and the spatial conflict between new subway engineering and existing municipal pipelines is increasingly prominent. In the process of project implementation, pipeline relocation is a conventional solution to such conflicts, and the foundation pit excavation operation often faces severe challenges: limited construction space, complex surrounding pipeline distribution, and difficulty in bringing in large mechanical equipment, which seriously affects the construction efficiency, cost, safety, and construction period. Most of the existing pipeline relocation foundation pit support and construction methods adopt two construction methods: 1) slope excavation method, which uses mechanical equipment to excavate step by step, and sprays anchor support on the slope; this construction method has the following problems: due to the use of mechanical construction, the site demand is large, the surrounding roads need to be excavated, and the construction period is long; the municipal pipeline network is complex, and the mechanical construction slope excavation method cannot effectively protect the unexplored pipelines; if the excavation depth is greater than 5m, the foundation pit still has the risk of collapse after the slope spray anchor support. 2) Steel sheet pile support method, steel sheet piles are set up on both sides of the pipeline, mechanical equipment is used for vertical excavation, and manual cleaning is used when excavating to 50cm above the pipeline; this construction method has the following problems: due to the use of steel plate, steel surrounding purlin, and steel support for support components, the construction needs to be coordinated with the crane, and the crane cannot be constructed under the overpass; and the unexplored pipelines cannot be protected during the steel sheet pile setting process. SUMMARY

[0003] The present application aims to provide a pipeline relocation foundation pit support and construction method in complex environment to solve the problem that the existing pipeline relocation foundation pit support and construction method cannot meet the construction requirements when encountering complex urban space.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] A pipeline relocation foundation pit support and construction method in complex environment, comprising the following steps:

[0006] S100, foundation pit structure design: the foundation pit comprises a plurality of serially connected rectangular wells, each well is connected into one body by two longitudinal arms and two transverse soil partitions, the arms are located on the side wall of the foundation pit, and the soil partitions are perpendicular to the arms; the soil partitions are provided with pipeline holes, the pipeline holes are circular holes with a diameter of d, the height of the soil partition is b, and the length of the soil partition is L, the diameter d of the pipeline hole should be smaller than the minimum value of the height b of the soil partition or the length L of the soil partition; the bottom of the well is further provided with a bottom seal, and the bottom seal is arranged below 0.5m below the pipeline hole;

[0007] S200, foundation pit excavation construction: the foundation pit is excavated by artificial partition well construction, that is, the single well structure is constructed first when excavating, and the double well structure is constructed after the bottom of the single well is completed; each well is excavated in construction sections, and the work is cycled down section by section, and the excavation depth of each construction section is 0.8-1.0m;

[0008] S300, foundation pit support construction: the construction is carried out by step-by-step support, and the arm of each construction section of the foundation pit is formed by binding a plurality of vertical main reinforcement and horizontal distribution reinforcement;

[0009] S400, foundation pit bottom sealing: layer-by-layer pouring of concrete;

[0010] S500, pipeline relocation:

[0011] S501, opening a pipeline hole in the earth partition wall;

[0012] S502, installing the pipeline: installing the changed pipeline into the pipeline hole.

[0013] Further, in step S100, the pipeline hole diameter, the pipeline hole position range, the earth partition wall thickness, and the arm thickness are calculated as follows:

[0014] S101, calculation of pipeline hole diameter

[0015] The pipeline hole diameter d should be less than the minimum value of the earth partition wall height b or the earth partition wall length L, and the formula is as follows:

[0016] d≤0.45min(b,L) ①

[0017] Wherein: the pipeline hole diameter is d, m; the earth partition wall height is b, m; the earth partition wall length L, m;

[0018] S102, calculation of pipeline hole position range

[0019] Horizontal position: assuming that the center horizontal point of the pipeline hole is x, the length of the earth partition wall is L, and the minimum edge distance from the edge of the pipeline hole to the left or right edge of the earth partition wall is m, then the horizontal position of the pipeline hole is:

[0020]

[0021] Wherein: the pipeline hole diameter is d, m; the earth partition wall length is L, m; the minimum edge distance from the edge of the pipeline hole to the left or right edge of the earth partition wall is m, m; the center horizontal point of the pipeline hole is x, m;

[0022] Vertical position: let the vertical point of the pipe hole center be y, the height of the earth retaining wall be b, and the minimum edge distance from the pipe hole edge to the top of the earth retaining wall or the edge of the bottom sealing be n, then the vertical position of the pipe hole is:

[0023]

[0024] wherein: the pipe hole diameter is d, m; the height of the earth retaining wall is b, m; the minimum edge distance from the pipe hole edge to the top of the earth retaining wall or the edge of the bottom sealing is n, m; the vertical point of the pipe hole center is y, m;

[0025] S103, calculation of the thickness of the earth retaining wall

[0026] The thickness of the earth retaining wall is related to the length of each section of the foundation pit and the index of the soil body, and needs to ensure that it can withstand the earth pressure and remain stable, and the thickness of the earth retaining wall is calculated as follows:

[0027] The thickness of the earth retaining wall t needs to meet the bending and shearing requirements, and the formula is:

[0028]

[0029] wherein: f c is the compressive strength of concrete, kPa; b is the height of the earth retaining wall, m; P is the earth pressure, kN; L is the length of the earth retaining wall, m; and a is the adjustment coefficient, dimensionless;

[0030] The earth pressure P is calculated according to the following formula:

[0031]

[0032] wherein: K is the earth pressure coefficient; H is the depth of the foundation pit, m; and γ is the unit weight of the soil, kN / m 2 ;

[0033]

[0034] wherein: is the internal friction angle of the soil, °;

[0035] S104, calculation of the thickness of the arm

[0036] The thickness of the arm t c needs to meet the bending and shearing requirements, and the formula is:

[0037]

[0038] wherein: f c is the compressive strength of concrete, kPa; h is the height of the arm, m; P is the earth pressure, kN; S is the length of the arm, m; and β is the adjustment coefficient, dimensionless;

[0039] If the height of the soil retaining wall or the arm is different in the same foundation pit, the height with the larger value is taken for calculation.

[0040] Further, in step S200, before excavation, the settlement monitoring points are arranged around the foundation pit, the settlement monitoring points are arranged on the outer edges of the rectangular wells connected in series, one monitoring point is arranged on the soil retaining wall at the head and tail ends, and at least one monitoring point is arranged on the arm of each well, and the road surface settlement control value of the foundation pit is less than 30 mm.

[0041] Further, after the monitoring point arrangement in step S200, before the foundation pit excavation construction, the lock hole construction is further included, and the lock hole construction includes:

[0042] S201, according to the size of the arm, the position of the pipeline is fitted in the plan, the corner points of the four construction sections of the excavated foundation pit are measured through construction lofting;

[0043] S202, steel drillings are buried at the corner points and are reinforced and protected by mortar, and the road surface is broken after the lofting is completed;

[0044] S203, after the road surface breaking is completed, the lock hole is constructed, the top surface of the lock hole is flat, the width is 0.6-0.8 m, the thickness is 0.2-0.4 m, the height is 300-400 mm higher than the original ground, and the concrete is cast in place.

[0045] Further, the pipe hole around the pipe hole is reinforced by using a grid steel frame or an I-steel.

[0046] Further, in step S300, the arm is a concrete arm, the arm concrete pouring is performed after each construction section is excavated, the strength of the concrete is greater than c25, and the formwork is removed after 12 hours of the concrete pouring or when the strength reaches 2.5 Mpa.

[0047] Further, in step S100, the steel ring is arranged on the soil retaining wall at the original pipe hole, and the steel ring is filled with plain concrete.

[0048] Further, in the pipeline relocation in step S500, step S501 can also be: removing the plain concrete in the steel ring on the soil retaining wall to obtain a steel pipe hole.

[0049] In summary, the beneficial effects of the present application are:

[0050] 1. The application is suitable for long strip-shaped narrow foundation pits in the case that the construction site is small in space, the surrounding pipelines are complex in distribution, and machinery cannot be used. The foundation pit is divided into multiple serial rectangular wells, each well is connected into a force whole by a transverse soil partition wall and a longitudinal arm, the soil partition wall provides transverse support force for the foundation pit, which is equivalent to the transverse support in the ordinary foundation pit support, and the arm provides lateral support force for the foundation pit, which is equivalent to the enclosure pile in the ordinary foundation pit support. In the construction of long strip-shaped narrow foundation pits, the structure can evenly disperse the load, effectively resist the lateral pressure of the soil body, ensure that the foundation pit is not easy to deform, settle and collapse, provide a foundation for the subsequent foundation construction, and guarantee the quality and durability of the whole project. Meanwhile, the well type construction method shows high flexibility for complex site conditions and special foundation pit shapes, is not limited to multiple wells in series, can flexibly adjust the size and number of rectangular wells according to the actual situation, adapts to different geological conditions and construction requirements, and can better cope with various complex construction scenes compared with the traditional construction method.

[0051] 2. In the design of the foundation pit, the correlation of the hole diameter on the soil partition wall with the height and length indicators of the soil partition wall is obtained to obtain the calculation formula relationship of the pipe hole diameter, and the safety range of the hole opening position of the pipe hole is limited. In the thickness calculation of the soil partition wall, the correlation of the thickness of the soil partition wall with the soil body indicators such as the compressive strength of concrete and soil pressure, and the structure indicators such as the height of the soil partition wall and the length of the soil partition wall is found to obtain the thickness calculation formula of the soil partition wall. In the thickness calculation of the arm, the correlation of the thickness of the arm with the soil body indicators such as the compressive strength of concrete and soil pressure, and the structure indicators such as the height of the arm and the length of the arm is found to obtain the thickness calculation formula of the arm.

[0052] 3. The foundation pit adopts the construction method of step-by-step excavation and step-by-step support, which can effectively control the ground settlement and deformation of the surrounding buildings, reduce the collapse risk, and also can adjust the support scheme according to the geological conditions to enhance the adaptability of the construction and ensure the smooth construction.

[0053] In summary, the application does not use large mechanical equipment, has no clearance requirement, can protect the pipeline and reduce the influence of the pipeline to the minimum, and through the step-by-step excavation and step-by-step pouring of the arm construction process, the foundation pit arm forms a whole structure, the foundation pit has high stability and is not easy to collapse. The settlement monitoring points are arranged in the foundation pit, and the real-time monitoring in the construction process verifies that the foundation pit designed and constructed by the method meets the design settlement requirements. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is the pipeline relocation foundation pit support and construction method flowchart in the complex environment of the application;

[0055] Figure 2 is the foundation pit structure elevation view in the complex environment of the application;

[0056] Figure 3 is the complex environment pipeline relocation foundation pit structure profile of the present application;

[0057] Figure 4 is the complex environment pipeline relocation foundation pit structure plan of the present application;

[0058] Wherein: 100 - foundation pit, 110 - No. 1 well, 120 - No. 2 well, 130 - No. 3 well, 140 - No. 4 well, 150 - earth diaphragm wall, 151 - steel ring, 160 - arm protection, 170 - bottom sealing, 200 - pipeline area, 210 - original pipeline, 220 - changed pipeline, 300 - underground passage, DB1.1 - No. 4 well earth diaphragm wall monitoring point, DB1.2 - No. 4 well arm protection monitoring point, DB1.3 - No. 3 well arm protection monitoring point, DB1.4 - No. 2 well arm protection monitoring point, DB1.5 - No. 1 well arm protection monitoring point, DB1.6 - No. 1 well earth diaphragm wall monitoring point, DB1.7 - No. 1 well arm protection monitoring point, DB1.8 - No. 2 well arm protection monitoring point, DB1.9 - No. 3 well arm protection monitoring point. DETAILED DESCRIPTION

[0059] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments given here are only for the purpose of illustrating and explaining the present application, and cannot be used to limit the present application.

[0060] It should be noted that in the following description, many specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can also have other embodiments and variations, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0061] The underground excavation underground passage 300 of the track traffic overpass station of the embodiment of the application has an original pipeline 210 above it, the original pipeline 210 conflicts with the structure section of the underground excavation underground passage 300 of the track traffic overpass station, and the path of the original pipeline 210 needs to be permanently relocated; the original pipeline 210 needs to be relocated at the position under the overpass bridge, the net clearance under the overpass bridge is only 5 m, large equipment such as a crane and a pile machine cannot be used for assistance, and the construction range is under the urban trunk road motor lane, the daily vehicle flow is extremely large, the construction condition is complex, the inner diameter of the original pipeline 210 to be relocated is 0.8 m, the buried depth is 5.5 m, in order to facilitate subsequent pipeline relocation construction, a personnel working space of more than 0.5 m needs to be arranged on both sides of the pipeline, therefore, the width of the foundation pit 100 needs to be more than 1.8 m; the cross-sectional length of the underground excavation overpass passage is 7.7 m, which provides a cutting and welding space for subsequent pipeline relocation, the length of the foundation pit 100 needs to be more than 10.8 m, and the internal dimensions of the foundation pit 100 are designed to be 12.2 m in length and 1.9 m in width according to the actual construction needs of the site, the foundation pit 100 is divided into a first well 110, a second well 120, a third well 130 and a fourth well 140, and the four wells are of the same size, each well has a length of 2.9 m and a width of 1.9 m, the first well 110 has a depth of 4.8 m, the second well 120 has a depth of 4.8 m, the third well 130 has a depth of 5.8 m, and the fourth well 140 has a depth of 6.4 m.

[0062] As shown in Figures 1-4 A pipeline relocation foundation pit support and construction method in a complex environment, comprising the following steps:

[0063] S100, foundation pit structure design

[0064] Due to the small construction site space, machinery cannot be used, and the pipeline foundation pit 100 is a long and narrow foundation pit 100, under these complex construction conditions, a long and narrow foundation pit 100 is formed in the form of a plurality of rectangular wells connected in series, a transverse soil partition wall 150 and an arm 160 are arranged on a single well, the transverse soil partition wall 150 is a transverse support of the foundation pit 100 formed perpendicular to the length direction of the foundation pit 100, which divides the long and narrow foundation pit 100 into a plurality of small rectangular areas, reduces the soil range of single excavation, and reduces the construction risk; the arm 160 is a concrete structure poured on the surface of the side wall of the foundation pit 100, which enhances the stability of the side wall of the foundation pit 100 and prevents soil collapse;

[0065] The foundation pit 100 comprises a plurality of rectangular wells connected in series, the wells are connected by two rows of arms 160 and two rows of earth retaining walls 150, the arms 160 are located on the side walls of the foundation pit 100, the earth retaining walls 150 are perpendicular to the arms 160, the bottom of the well is also provided with a bottom sealing 170, the earth retaining wall 150 is provided with a pipeline hole (not shown in the figure), the pipeline hole is a circular hole with a diameter of d, the height of the earth retaining wall 150 is b, the length of the earth retaining wall 150 is L, the diameter d of the pipeline hole should be smaller than the minimum value of the height b of the earth retaining wall or the length L of the earth retaining wall, and the bottom sealing 170 is arranged below the pipeline hole by 0.5 m;

[0066] In step S100, the reasonable limitation of the diameter of the pipeline hole is usually related to the height of the retaining wall, the strength of the wall material, the load distribution and the structural stability. In actual engineering, if the opening size is too large, the stiffness of the wall will decrease, which will affect the overall stability of the structure, so it is necessary to strictly control the opening size. In order to ensure the safety of the foundation pit, the calculation of the diameter of the pipeline hole, the position range of the pipeline hole, the thickness of the earth retaining wall 150 and the thickness of the arm 160 is as follows:

[0067] S101, calculation of the diameter of the pipeline hole

[0068] The diameter d of the pipeline hole should be smaller than the minimum value of the height b of the earth retaining wall 150 or the length L of the earth retaining wall 150, and the formula is as follows:

[0069] d≤0.45min(b,L) ①

[0070] Wherein: the diameter of the pipeline hole is d, m; the height of the earth retaining wall is b, m; the length of the earth retaining wall L, m;

[0071] In this embodiment, the width of each well, i.e. the length L of the earth retaining wall 150, is 1.9 m, the minimum depth of the foundation pit 100, i.e. the height b of the earth retaining wall 150, is 4.8 m, and the minimum value of the length L of the earth retaining wall 150 is 1.9 m, so the diameter d of the pipeline hole is:

[0072] d≤0.45×1.9≤0.86m

[0073] The diameter d of the pipeline hole is 0.85 m, the inner diameter of the original pipeline 210 to be relocated is 0.8 m, and 0.8 m≤0.85 m, so the diameter d of the pipeline hole meets the installation diameter requirement of the original pipeline to be relocated;

[0074] The position range of the pipeline hole is as follows:

[0075] Horizontal position: assuming that the horizontal center point of the pipeline hole is x, the length of the earth retaining wall 150 is L, and the minimum edge distance from the edge of the pipeline hole to the left or right edge of the earth retaining wall 150 is m, then the horizontal position of the pipeline hole is:

[0076]

[0077] Wherein: the pipe hole diameter is d, m; the earth dike 150 length is L, m; the minimum edge distance from the pipe hole edge to the left or right edge of the earth dike 150 is m, m; the pipe hole center horizontal point is x, m;

[0078] In this embodiment, the well width, i.e. the earth dike 150 length L, is known to be 1.9 m, the pipe hole diameter d is taken as 0.85 m, and the minimum edge distance m from the pipe hole edge to the left or right edge of the earth dike 150 is taken as 0.2 m, so the pipe hole horizontal position is:

[0079]

[0080] 0.63 m≤x≤1.28 m

[0081] To ensure that a personnel working space of 0.5 m or more is provided on both sides of the pipe, the pipe hole horizontal position is taken as 0.95 m;

[0082] Vertical position: assuming the pipe hole center vertical point is y, the earth dike 150 height is b, and the minimum edge distance from the pipe hole edge to the top or bottom edge of the earth dike 150 is n, the pipe hole vertical position is:

[0083]

[0084] Wherein: the pipe hole diameter is d, m; the earth dike height is b, m; the minimum edge distance from the pipe hole edge to the top or bottom edge of the earth dike 150 is n, m; the pipe hole center vertical point is y, m;

[0085] In this embodiment, the earth dike 150 height b1 of the No. 1 well 110 and the earth dike 150 height of the No. 2 well 120 are both known to be 4.8 m, the earth dike 150 height b3 of the No. 3 well 130 is 5.8 m, the earth dike 150 height b4 of the No. 4 well 140 is 6.4 m, the pipe hole diameter d is taken as 0.85 m, and the minimum edge distance n from the pipe hole edge to the top or bottom edge of the earth dike 150 is taken as 0.5 m, so the pipe hole vertical positions of the No. 1 well 110, the No. 2 well 120, the No. 3 well 130, and the No. 4 well 140 are:

[0086] The pipe hole vertical position y1 of the No. 1 well 110 and the No. 2 well 120 is:

[0087]

[0088] 0.83 m≤y1≤3.98 m

[0089] The vertical position of the pipeline hole of the third well 130 is y3:

[0090]

[0091] 0.83m≤y3≤4.98m

[0092] The vertical position of the pipeline hole of the fourth well 140 is y4:

[0093]

[0094] 0.83m≤y4≤5.58m

[0095] In the embodiment, for the convenience of construction, the vertical position of the pipeline hole of the first well 110, the second well 120, the third well 130, and the vertical position of the pipeline hole on the earth retaining wall 150 connected with the third well 140, i.e., the vertical position y of the pipeline hole from the top of the earth retaining wall 150 to the upper edge of the pipeline hole, is 3m. a The vertical position of the pipeline hole on the other side of the earth retaining wall 150 of the fourth well 140, i.e., the vertical position y of the pipeline hole from the top of the earth retaining wall 150 to the upper edge of the pipeline hole, is 5.2m. b The vertical position of the pipeline hole on the other side of the earth retaining wall 150 of the fourth well 140, i.e., the vertical position y of the pipeline hole from the top of the earth retaining wall 150 to the upper edge of the pipeline hole, is 5.2m.

[0096] The thickness of the earth retaining wall 150 and the thickness of the arm 160 are calculated as follows:

[0097] S103, calculation of the thickness of the earth retaining wall

[0098] The thickness of the earth retaining wall is related to the length of each foundation pit and the index of the soil body, and needs to ensure that it can withstand the earth pressure and remain stable. The calculation steps of the thickness of the earth retaining wall are as follows:

[0099] The thickness t of the earth retaining wall needs to meet the requirements of bending resistance and shear resistance, and the formula is:

[0100]

[0101] Wherein: f c is the compressive strength of concrete, kPa; b is the height of the earth retaining wall, m; P is the earth pressure, kN; L is the length of the earth retaining wall, m; and a is the adjustment coefficient, dimensionless.

[0102] The earth pressure P is calculated according to the following formula:

[0103]

[0104] Wherein: K is the earth pressure coefficient; H is the depth of the foundation pit, m; and γ is the unit weight of the soil body, kN / m 2 ;

[0105]

[0106] wherein: is the internal friction angle of soil, °;

[0107] It is known that each of the well width, i.e. the length L of the earth retaining wall 150, is 1.9 m, the depth of the foundation pit 100, i.e. the height b of the earth retaining wall 150, is 6.4 m, the adjustment coefficient a is 602.01, the compressive strength f c Take 17860 kPa, the internal friction angle of soil is 25 °;

[0108] First, calculate the earth pressure coefficient K:

[0109]

[0110] Then calculate the earth pressure P:

[0111]

[0112] Get the thickness t of the earth retaining wall 150:

[0113]

[0114] In this embodiment, the thickness t of the earth retaining wall 150 is 0.3 m;

[0115] S104, the thickness of the arm is calculated

[0116] The thickness t of the arm c The bending and shear requirements need to be met, and the formula is:

[0117]

[0118] wherein: f c is the compressive strength of concrete, kPa; h is the height of the arm, m; P is the earth pressure, kN; S is the length of the arm, m; β is the adjustment coefficient, dimensionless;

[0119] wherein: f c is the compressive strength of concrete, kPa; h is the height of the arm, m; P is the earth pressure, kN; S is the length of the arm, m; β is the adjustment coefficient, dimensionless;

[0120] If the height of the earth retaining wall or the arm in the same foundation pit is different, the larger height is taken for calculation.

[0121] It is known that each of the well length L, i.e. the length S of the arm 160, is 2.9 m, the depth of the foundation pit 100, i.e. the height h of the arm 160, is 6.4 m, the earth pressure P is about 159.89 kN; the compressive strength f c Take 17860 kPa, the adjustment coefficient β is 473.31; the thickness t of the arm 160c For:

[0122]

[0123] In this embodiment, the thickness t of the arm 160 is 0.3m c Take 0.3m;

[0124] S200, foundation pit excavation construction: the foundation pit 100 is constructed by artificial isolation well excavation, that is, when excavating, the odd well structure is constructed first, and after the concrete bottom sealing 170 of the odd well is completed, the even well structure is constructed; each well is excavated in construction sections, and the work is cycled down section by section, and the excavation depth of each construction section depends on the ability of the hole wall self-stability state, and the excavation depth of each construction section is 0.8-1.0m, and the excavation depth is reduced when special geological conditions are encountered;

[0125] S300, foundation pit support construction: the construction is constructed by step-by-step support, and the arm 160 of each construction section of the foundation pit 100 includes vertical main reinforcement and horizontal distribution reinforcement, the vertical main reinforcement adopts Φ14@250 steel bars; the horizontal distribution reinforcement adopts Φ14@250 steel bars when the excavation depth is 0-3m, and adopts Φ16@250 steel bars when the excavation depth is 3-7.5m, and a construction section support is formed by binding the vertical main reinforcement and the horizontal distribution reinforcement; in step S300, the arm 160 is a concrete arm, and after the excavation of each construction section is completed, the arm 160 is poured with concrete, and the strength of the concrete is greater than c25; the formwork is removed after 12h of pouring concrete, or when the strength reaches 2.5Mpa;

[0126] S400, foundation pit concrete bottom sealing

[0127] S401, cleaning the foundation pit: removing sundries, accumulated water and loose soil;

[0128] S402, installing the formwork: installing the formwork according to the design requirements;

[0129] S403, pouring concrete: pouring in layers, and the thickness of each layer is controlled to be 30-50cm, and the concrete is vibrated and compacted;

[0130] S404, removing the formwork: removing the formwork after the strength of the concrete reaches the design requirements;

[0131] S500, pipeline relocation

[0132] S501, opening the pipeline hole of the earth retaining wall 150: according to the design drawing, the position and size of the pipeline hole are marked on the earth retaining wall 150, several small holes are drilled in the outline of the pipeline hole, the holes are drilled along the outline using an electric drill or an impact drill, the wall body between the holes is chiseled out using a tool, and the hole is gradually enlarged until the hole opening is completed;

[0133] S502. Install the pipe: Install the modified pipe 220 into the pipe hole.

[0134] like Figure 4 As shown, in step S200, in order to determine the impact of the excavation process on the settlement of the surrounding roads, settlement monitoring points are set up in the foundation pit 100 before excavation. The settlement monitoring points are set on the outer edge of the rectangular wells connected in series in the foundation pit 100. One monitoring point is set up at each of the soil partition walls 150 at the first and last ends. At least one monitoring point is set up on the guard arm 160 of each well. The road surface settlement control value of the foundation pit 100 is less than 30mm.

[0135] In this embodiment, the foundation pit 100 is divided into wells 1-4. A monitoring point is set on the soil partition wall 150 at the beginning and end of wells 1 and 4. A monitoring point is set on the guard arm 160 on both sides of wells 1-3. A monitoring point is set on the guard arm 160 on one side of well 4, for a total of 9 monitoring points. The entire process is monitored during the excavation, and the monitoring frequency is twice a day.

[0136] The excavation of foundation pit 100 was divided into four stages: excavation of construction sections 1 and 3, bottom sealing of construction sections 1 and 3 at 170mm, excavation of construction sections 2 and 4, and bottom sealing of construction sections 2 and 4 at 170mm. With the bottom sealing of all four construction sections at 170mm completed, the entire foundation pit 100 retaining wall 160 became a whole. The lateral earth pressure was converted into bending moment of the retaining wall 160, which acted on the bottom concrete sealing 170mm. The entire stress system was stable, and the monitoring data showed no significant changes. Therefore, this stage was not analyzed separately. The analysis of the other stages is shown in the table below.

[0137]

[0138]

[0139] Based on the test data in the table above, it can be inferred that during each construction stage of the pipeline pit 100 excavation, the settlement values ​​of the surrounding roads at each measuring point did not reach the yellow warning level, i.e., 70% of the road surface settlement control value of 30mm. This proves that the pipeline relocation pit 100 support and construction method of the present invention meets the requirements for settlement of the surrounding roads during the pipeline pit 100 excavation process, and the structure is in a stable state.

[0140] In actual construction, after the monitoring points are set up in step S200 and before the excavation of the foundation pit 100, the construction of keyholes is also included. The construction of keyholes includes:

[0141] S201. Based on the design of the 160mm guard arm, the pipe position is overlaid on the plan. Through construction layout, the corner points of the four construction sections of the 100mm excavation pit are measured.

[0142] S202. Steel rods are embedded at the corner points and reinforced with mortar. After the layout is completed, the road surface is broken up using demolition equipment. During the demolition process, steel rods are used to pull the diagonal line for dimension correction to ensure that the clearance dimension and the thickness of the guard arm 160 meet the requirements.

[0143] S203. After the road surface is demolished, construct the manhole cover to prevent rainwater from flowing into the manhole and to prevent the manhole cover from sinking when the next section of the manhole wall is excavated; the top surface of the manhole cover is flat, 0.7m wide, 0.3m thick, and slightly higher than the original ground surface by 300mm, and is cast in place using C35 concrete.

[0144] In practice, the pipe opening is reinforced with a grating steel frame or I-beams.

[0145] like Figure 3 As shown, in step S100, a steel ring 151 is provided at the original pipe hole on the soil partition wall 150, and plain concrete is filled inside the steel ring 151 to ensure the integrity of the soil partition wall 150.

[0146] In actual construction, during the pipeline relocation in step S500, step S501 can also be: removing the plain concrete inside the steel ring on the soil partition wall to obtain a steel pipe hole, thus eliminating the drilling step and saving construction time.

[0147] It should be understood that the above embodiments are one or more embodiments of the present invention, and there are many other embodiments and variations based on the present invention; any variations and modifications made by those skilled in the art through the present invention without making pioneering innovations are all within the protection scope of the present invention.

Claims

1. A construction method for supporting a foundation pit for pipeline relocation in a complex environment, characterized in that, The method comprises the following steps: S100, foundation pit structure design: the foundation pit comprises a plurality of rectangular wells connected in series, each well is connected into one body by two longitudinal arms and two transverse soil partitions, the arms are located on the side walls of the foundation pit, and the soil partitions are perpendicular to the arms; the soil partitions are provided with pipeline holes, the pipeline holes are round holes; the bottom of the well is further provided with a bottom sealing part, the bottom sealing part is arranged below the pipeline holes by 0.5 m or more; the height of the soil partition is b m; the length of the soil partition is L m; the diameter of the pipeline hole is d m; The calculation method of the diameter of the pipeline hole, the position range of the pipeline hole, the thickness of the soil partition and the thickness of the arm is as follows: S101, calculation of the diameter of the pipeline hole: The diameter of the pipeline hole is smaller than the minimum value of the height of the soil partition and the length of the soil partition, and the formula is as follows: ① S102, calculation of the position range of the pipeline hole: Horizontal position: the center horizontal point of the pipeline hole is x, the minimum edge distance from the edge of the pipeline hole to the left or right edge of the soil partition is m, and the horizontal position of the pipeline hole is: ② Vertical position: the center vertical point of the pipeline hole is y, the minimum edge distance from the edge of the pipeline hole to the top or bottom edge of the soil partition is n, and the vertical position of the pipeline hole is: ③ S103, calculation of the thickness of the soil partition The thickness of the soil partition is related to the length of each section of the foundation pit and the soil index, so as to ensure that the soil partition can bear the soil pressure and remain stable, The calculation steps of the thickness of the soil partition are as follows: The thickness of the soil partition t needs to meet the bending and shearing requirements, and the formula is: ④ wherein: Pc is the compressive strength of the concrete, kPa; P is the earth pressure, kN; and a is an adjustment factor, dimensionless. The soil pressure P is calculated according to the following formula: ⑤ wherein: K is the earth pressure coefficient; H is the depth of the foundation pit, m; is the bulk density of the soil, kN / m 2 ; )； wherein: is the internal friction angle of the soil, °; S104, calculation of the thickness of the arm: Arm thickness The bending and shear requirements must be satisfied, and the formula is: ⑥ wherein: = concrete compressive strength, kPa; h = height of the arm, m; P = earth pressure, kN; S = length of the arm, m; β = adjustment factor, dimensionless. If the heights of the soil partitions or the arms in the same foundation pit are different, the maximum height is taken for calculation; S200, foundation pit excavation construction: the foundation pit is constructed by artificial well isolation excavation, that is, when excavating, the single well structure construction is first performed, and after the bottom sealing of the single well is completed, the double well structure construction is performed; each well is excavated in construction sections, and the operation is circularly performed section by section, and the excavation depth of each construction section is 0.8-1.0 m; S300, foundation pit support construction: the construction is performed by step-by-step support, and the arm of each construction section of the foundation pit is formed by binding a plurality of vertical main reinforcement and horizontal distribution reinforcement; S400, foundation pit bottom sealing: layer-by-layer pouring of concrete; S500, pipeline relocation: S501, soil partition pipeline hole opening; S502, pipeline installation: the changed pipeline is installed into the pipeline hole.

2. The method for supporting a foundation pit for pipeline relocation in a complex environment according to claim 1, characterized in that: In step S200, before excavation, settlement monitoring points are arranged around the foundation pit, the settlement monitoring points are arranged on the outer edges of the rectangular wells connected in series of the foundation pit, one monitoring point is arranged on the soil partition at the head and tail end respectively, at least one monitoring point is arranged on the arm of each well, and the road surface settlement control value of the foundation pit is less than 30 mm.

3. The method according to claim 2, wherein: After the settlement monitoring points are arranged in step S200, before the foundation pit excavation construction, lock opening construction is further included, and the lock opening construction comprises: S201, according to the arm size design, the pipeline position is fitted into the plan, the four corner points of the excavation foundation pit are measured by construction lofting; S202, steel pegs are buried at the corner points and are protected by mortar reinforcement, and the road surface is broken after the lofting is completed; S203, after the road surface breaking is completed, the lock is constructed, the top surface of the lock is flat, the width is 0.6-0.8m, the thickness is 0.2-0.4m, and the height is 300-400mm higher than the original ground, and the concrete is cast in situ.

4. The method for supporting a foundation pit for pipeline relocation in a complex environment according to claim 3, characterized in that: The pipe hole hole mouth is strengthened by using a grid steel frame or an I-steel around the pipe hole hole mouth.

5. The method for supporting a foundation pit for pipeline relocation in a complex environment according to claim 1, characterized in that: In step S300, the arm is a concrete arm, and after each construction section is excavated, the arm concrete is poured, and the arm concrete strength is greater than c25.

6. The method for supporting a foundation pit for pipeline relocation in a complex environment according to claim 1, characterized in that: In step S100, a steel ring is arranged at the pipe hole of the earth diaphragm wall, and the steel ring is filled with plain concrete.

7. The method of claim 6, wherein the method further comprises: providing a plurality of support structures; and positioning the plurality of support structures in the trench. In step S500 of the pipeline relocation, step S501 is to remove the plain concrete in the steel ring of the earth diaphragm wall to obtain the pipe hole.

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